From a short barrel, loadings with heavy bullets are actually the most efficient. This is because it takes more pressure to push a heavier bullet out of the case than a light one and thus a greater percentage of the powder is burned inside the case rather than in the barrel. This also means that, with a short barrel, a smaller percentage of the powder burns after the bullet has already left the barrel and thus velocity "loss"...............
why bring that up?? is powder burning efficieny at all meaningfull if you are trying to kill an violent intruder??? if the 125 g moves a bit snappier through drywall why even mention efficiency of so-called powder burn....if that is a 'myth' to begin with.